It is well-known in the art that certain materials called phosphors can be irradiated with high energy ionizing radiation, and then subsequently stimulated to produce an emission. In the case of thermoluminescent phosphors the stimulation is heat which causes release of the stored ionization energy in the form of a visible light emission commonly called a thermoluminescent emission. Thermoluminescent phosphors are currently in widespread use in radiation dosimeters used to measure the amount of incident radiation to which people, animals, plants and other things are exposed. Thermoluminescent dosimeters are widely used by workers in the nuclear industries to provide a constant monitor for measuring exposure to radiation.
Phosphors are excited by energetic radiation such as ultraviolet, X-ray, gamma, and other forms of radiation. Such ionizing radiation causes electrons within the phosphor material to become more highly energized. The nature of the phosphor materials causes these high energy electrons to be trapped at relatively stable higher energy levels. The electrons stay at these higher energy levels until additional energy, often in the form of heat, is supplied which releases the trapped electrons, thereby allowing them to fall back to a lower energy state. The return of the electrons to a lower energy state causes a release of energy primarily in the form of visible light which is ordinarily termed a luminescent emission. Emission can also occur from phosphors in other energy forms other than visible light although such alternative emissions are not typically used at this time.
The widespread use of thermoluminescent phosphors in personnel dosimeters has led to demand for a large number of dosimeters which must be read on a routine basis in order to monitor exposure of persons or other objects to ionizing radiation. Because of the substantial numbers and the relatively slow reading techniques currently employed, the job of reading dosimeters becomes very time consuming and costly.
There are four commonly known methods of heating thermoluminescent material in order to release the trapped electrons and provide the luminescent emission which is measured as an indication of the amount of ionizing radiation to which the dosimeter was exposed. The first and most common method for heating thermoluminescent phosphors is by contact heating. The second method is heating using a hot gas stream which is impinged upon the phosphor. The third method uses radiant energy in the form of infrared beams which heat the thermoluminescent phosphor. The fourth method uses laser beams to provide the necessary heat or other stimulus for luminescent emission.
In addition to the heat stimulation of phosphors it is also possible to stimulate them with laser beams in a phenomenon call optically stimulated luminescence. In optically stimulated luminescence the laser beam is directed in an intense beam having high power for very brief periods of time. This form of laser stimulation is explained in U.S. Pat. No. 4,507,562 which is hereby incorporated by reference.
The phosphors are incorporated into dosimeters which are mounted in a variety of ways in dosimeter badges. It is preferably that the dosimeters be protected from light, moisture, dust and mechanical deterioration. Light can affect the radiation dose readings given by the dosimeters. Moisture can lead to the deterioration of the phosphor. Dust contamination can lead to incandescence of the contaminating dust particles during laser and other types of heating. Accordingly, it is preferably that dosimeter badges be constructed to protect and enclose the dosimeter elements in a sealed interior compartment.
The monitoring of personnel radiation exposure also suggests the need for personnel dosimeter badges which are tamper resistant so that the wearer or others do not cause changes in the measured dose or damage to the dosimeter elements. Since dosimeter badges can be worn in some applications for periods up to approximately one month before reading is necessary, the desirability of proper protection, containment, and tamper resistance of the dosimeter elements is apparent.
These and other factors have lead to the development of improved dosimeter badges by one of the inventors and his colleagues which include two detachable parts which contain a plurality of dosimeter elements of differing types. Such novel dosimeter badges are described in the U.S. patent application Ser. No. 343,000 described and incorporated by reference hereinabove. The dosimeter elements are preferably maintained in a sealed compartment free from moisture, dust, light and tampering. Because of the desirability of sealed containment of the dosimeters it thus becomes necessary to disassembly the sealed badges to gain access for stimulation of the phosphor-containing dosimeters held within the badges. When such novel dosimeters are read using laser beams or other means, it is thus typically necessary to separate the complementary parts of the dosimeter badge to expose the dosimeter elements for stimulation of the phosphor and detection of the luminescent or other emission caused by such stimulation. The emission is then used to indicate the amounts and types of ionizing radiation to which the dosimeter element was exposed. The large number of badges which must be read causes substantial amounts of time to be consumed in merely disassembling and reassembling the dosimeter badges, aside from the time needed to read the phosphors.
The current invention relates to improved methods and apparatuses for assembling and disassembling dosimeter badge components which aid in the automated handling and reading of such badges. The invention includes improved methods, tools, dosimeter badge assembly and disassembly apparatuses, and dosimeter reading apparatuses which incorporate them.